Establishing controlled airspace

[soaringhigh650]

For your area, how and when does controlled airspace get established?

Do they get drawn up when traffic reaches a certain density, and/or around 'blackspots' with a history of mid-air collisions?

Who proposes them? Is it the pilots themselves or the airport or the government?

Do upgrades (say from Charlie to Bravo) happen where traffic density continue to increase and vice versa?

Has its effects been positive as a whole (ie. reduced near-misses with other stuff)?

 

[gismo]

For your area, how and when does controlled airspace get established?

Do they get drawn up when traffic reaches a certain density, and/or around 'blackspots' with a history of mid-air collisions?

Who proposes them? Is it the pilots themselves or the airport or the government?

Do upgrades (say from Charlie to Bravo) happen where traffic density continue to increase and vice versa?

Has its effects been positive as a whole (ie. reduced near-misses with other stuff)?

If by "controlled airspace" you mean Class B and C areas, I believe it's a combination of traffic levels and scheduled airline traffic. No doubt the FAA has specific thresholds of that which allow/require the establishment of approach control radar (the basis of Class B and C) and when those thresholds are exceeded they start the machinery to put such an area in place.

Other controlled airspace (Class E) exists over much of the continental US higher 700 or 1200 AGL with occasional portions touching the ground in what used to be called a "control zone". The lower limits of Class E are related to airways, the approaches and weather reporting at airport for the most part.

 

[BillTIZ]

Just went through that. There are traffic counts and rules to follow when setting up Class B and Class C airspace. FAA JO 7400.2G governs part of the airspace design process.